Reduce allocations in PENamedTypeSymbol.GetMemberTypesPrivate#81605
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CyrusNajmabadi merged 2 commits intodotnet:mainfrom Dec 11, 2025
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| int capacity = 0; | ||
| foreach (var typeArray in _lazyNestedTypes.Values) | ||
| { | ||
| capacity += typeArray.Length; | ||
| } | ||
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| var builder = ArrayBuilder<NamedTypeSymbol>.GetInstance(capacity); |
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Suggested change
| int capacity = 0; | |
| foreach (var typeArray in _lazyNestedTypes.Values) | |
| { | |
| capacity += typeArray.Length; | |
| } | |
| var builder = ArrayBuilder<NamedTypeSymbol>.GetInstance(capacity); | |
| var builder = ArrayBuilder<NamedTypeSymbol>.GetInstance(_lazyNestedTypes.Values.Sum(static a => a.Length)); |
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If we are doing the work to determine the exact capacity up front, then this would be better off just creating the array explicitly, rather than using an ArrayBuilder and hitting the pool, something like:
private ImmutableArray<NamedTypeSymbol> GetMemberTypesPrivate()
{
var count = _lazyNestedTypes.Values.Sum(static a => a.Length);
var result = new PENamedTypeSymbol[count];
var destIndex = 0;
foreach (var typeArray in _lazyNestedTypes.Values)
{
typeArray.CopyTo(result, destIndex);
destIndex += typeArray.Length;
}
return ImmutableCollectionsMarshal.AsImmutableArray<NamedTypeSymbol>(result);
}
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Updated to use explicit array.
Contributor
Could you link me to those ETW traces. You can read me internally if needed. |
333fred
approved these changes
Dec 10, 2025
CyrusNajmabadi
approved these changes
Dec 11, 2025
Contributor
|
Thanks! |
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